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Changes in the fractionation profile of Al, Ni and Mo during bioleaching of spent hydroprocessing catalysts with Acidithiobacillus ferrooxidans.
Pathak, Ashish; Healy, Mark G.; Morrison, Liam
Spent hydroprocessing catalysts are known to contain a variety of potentially toxic metals and therefore studies on the bioavailability and mobility of these metals are critical for understanding the possible environmental risks of the spent catalysts. This study evaluates the different chemical fractions/forms of aluminium (Al), nickel (Ni) and molybdenum (Mo) in spent hydroprocessing catalyst and the changes they undergo during bioleaching with Acidithiobacillus ferrooxidans. In the spent catalyst (prior to bioleaching), Al was primarily present in its residual form, suggesting its low environmental mobility. However, Ni comprised mainly an exchangeable fraction, indicating its high environmental mobility. Molybdenum was mainly in the oxidizable form (47.1%), which indicated that highly oxidizing conditions were required to liberate it from the spent catalyst. During bioleaching the exchangeable, reducible and oxidizable fractions of all the metals were leached, whereas the residual fractions remained largely unaffected. At the end of bioleaching process, the metals remaining in the bioleached sample were predominantly in the residual fraction (98.3-99.5%). The risk assessment code (RAC) and IR analysis also demonstrated that the environmental risks of the bioleached residue was significantly lower compared to the untreated spent catalyst. The results of the current study suggest that bioleaching is an effective method in removing the metals from spent catalysts and the bioleached residue poses little environmental risk. This work was supported by the Irish Research Council under grant GOIPD/2015/589. Dr Liam Morrison acknowledges the Science Foundation of Ireland (SFI) Research Professorship Innovative Energy Technologies for Biofuels Bioenergy and a Sustainable Irish Bioeconomy (IETSBIO3) research program to NUI, Galway. 2019-06-05
Keyword(s): Bioleaching; Fractionation; Metals; Spent Catalyst
Publication Date:
Type: Other
Peer-Reviewed: Yes
Language(s): English
Contributor(s): Irish Research Council; Science Foundation Ireland
Institution: NUI Galway
Publisher(s): Taylor & Francis
File Format(s): application/pdf
First Indexed: 2019-03-23 06:45:32 Last Updated: 2019-03-23 06:45:32